A modern capsule filling machine for making hard gelatin capsules normally comprises a rotary turret or carousel equipped with a plurality of operating stations for processing the capsules according to a standard method consisting of the following sequence of basic steps: opening the closed empty capsules at a station where the capsule bodies are separated from the lids to form two separate rows of bodies and lids; filling a predetermined quantity of pharmaceutical material in solid form into each capsule body at a dosing station; and closing each filled capsule by applying a lid to the respective body.
Once closed, the capsules are expelled from the carousel of the filling machine and fed into an appropriate container.
The capsules made in filling machines of this type also have to be weighed to ensure that they have been filled correctly. At present, this is done according to two different methods.
In a first method, the final weight of the capsules is checked statistically, that is to say, by taking samples of closed filled capsules and weighing them on electronic checkweighers connected to the central unit that controls and sets the quantities of solid pharmaceutical material to be filled into the capsule bodies.
Although this method is effective, it has an inherent disadvantage linked precisely to the statistical nature of the checkweighing system. Thus, if sample capsules failing outside the predetermined weight ranges are detected, a certain amount of time passes before the system corrects the dose of pharmaceutical material. This “time lag” means there is always the risk that a certain number of unchecked capsules of incorrect weight will be produced.
In an alternative method, the level of the pharmaceutical material dose filled into each capsule body is individually checked before the lids are applied to the respective bodies.
The pharmaceutical material level, from which the weight of each capsule is calculated, is checked using optical sensors.
These optical sensors, however, are difficult to control, involve complicated calibrating procedures and, above all, are not always capable of providing satisfactory readings of the level of solid material in the capsule bodies, with the result that many capsules passed by the sensors are in fact incorrectly filled, that is to say, are subsequently found to be faulty in weight.
The present invention therefore has for an aim to overcome the above mentioned disadvantages.
In particular, the present invention has for an aim to provide a capsule filling machine where the weight of all the capsules is checked in the filling process during a rapid, accurate operating step performed using a simple and effective instrument of mechanical type.